been following this one a lot lately.
What I do know is this--and some know all this anyway but I thought I'd compile it here:
1) UA + DL still as it was: not for international and not for codeshare or express. Just straight flights, and no stopovers. You call the airline from which you are taking the award to book on the other. That is unchanged.
2) slpflyer, get on it! take copies of all tickets, notes, boarding c\ards, etc and write em a letter simply explaining what you just said here. If all is correct there should be no time limit on this one. I have done domestic DL and UA flights that do take a while to credit but am on it til they do. I just have a folder kept handy with everything needed til I see my miles post.
I would not worry about NOT being allowe dto get UA miles on DL or DL miles on UA until THEY announce it, but keep records and be prepared to send copies in to whichever airline you want the miles on if they do not come in within a few weeks. Again: slpflyer
get on it! You will be fine.
3) yes, DL===>HH is ending and you need to get your DL miles out ASAP. They have to be sent to you so that the certs that DL mails you are dated before FEB 28. Dont wait til last minute! The miles are transferrable in 5k increments and take more than 60 days to credit to HH once they get them signed from your mailing to them. But yeah, you can check more relevant threads there. But we know all this.
4) US Air and UAL: you can get miles on both by flying both, but you cannot yet USE miles on either to fly either. I have heard APRIL. Many agents talked to said they believe it will include UAL express and code share flights but dont know yet. This may effect the DL relationship so I would imagine that things will change soon. However, right now, you can earn on 3 carriers in the US which is nice. take it while it lasts and just keep records.
5) Now, if you wanna try to send those boarding cards and ticket copies into partners overseas that you have FFp on... you can! You get the miles there or here... even for domestic flights. Just tell them you forgot to do it at the counter and be sure the miles are not already being credited to the local carrier.

MM
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If speed is not your thing, distance may as well be. Enjoy and embrace it all!